Translating system



' :TRANSLAT'ING SYSTEM Filed Jan. 16. 1928 .scnrcrt.

INVENTOR firrxraxz ex.

a 2 BY ATTORNEY Patented Apr. 21, 1931 UNITED STATES PATENT OFFlCE BERNARD J. KRIOGER, OF NEW YORK, N. Y., ASSIGNOR TO WESTINGHOUSE ELEUIBIC 4* MANUFACTURING COMPANY, A. CORPORATION OF PENNSYLVANIA TRANSLATING SYSTEM I Application filed January 16, 1928. Serial No. 247,030.

-My invention relates to translating systems, and more particularly to systems of the type known as talking movies, whereln sounds photographically recorded on a mo- 5 tion-picture film are subsequently reproduced during the operation of projecting the pictures.

By reason of the fact that, in the process of photographically recording the sounds ac- 1 companying a picture being filmed, it is inexpedient to move the microphone from place to place in order to follow the movements of the actors, the level of the recorded sounds has a tendency to vary much more 35 than is desirable. Furthermore, the chemical processes involved in the developing of the film, and in the developing of the positives printed therefrom, are not absolutely controllable, with the result that the film,

when finally prepared for projection, carries a sound record which may possibly not be truly representative of the volume of the original sounds.

In order to reproduce the photographically recorded sounds, light from a convenient source is caused to pass through a minor longitudinal portion of the movin film, and to thereafter fall upon a photo-e ectrio cell that is connected in the input circuit of an amplifying device comprising a plurality of thermionic tubes. The output current from the amplifying device is utilized to ener 'ize a sound-reproducing device, or loud speaher, preferably disposed either behind the screen a on which the picture is projected, or closely adjacent to the screen.

In order that the reproduction shall be pleasing to the audience, it is necessary that the sound shall, at no time, be excessively loud, and that it shall be substantially the same as would have been heard by an observial' at the location from which the picture was taken. To this end, sound-volume-control means, that may be manipulated from a position in the audience, is highly desirable.

It is also necessary, if an undistorted output is to be obtained from the sound reproducer or loud-speaker actuated by the aforementioned amplifying device, that the boundaries of the minor portion of the film momentarily exposed to the light shall be sharply defined. It has previously been proposed to limit that portion of the film instantaneously exposed to the light, both in recording and reproducing, by passing the film closely adjacent to a narrow slot, which slot, if desirable, may be provided with a glass or quartz filling. To be eflective, however, the slot must be given a width of not over .005 inch in the direction of film travel, and the light, in passing therethrough, is often diffracted to such an extent as to cause a noticeable distortion.

It is, accordingl an object of my invention to provide, in a translating system, means for satisfactorily controlling the intensity and the volume of the sound re roduced from a composite sound-picture lm.

Another object of my invention is to provide, in systems of the aforementioned type, instrumentalities for controlling the volume of the sound-output without introducing extraneous noises.

Another object of my invention is to pro vide, in a translating system, volume-com trol means that functions independently of the amplifying device.

Another ob ect of my invention is to pro- Vide, in systems of the aforementioned type, means for securing a sharp definition of that portion of the film which is instantaneously exposed to light, either in the recording or in the reproducing process.

Another object of my invention is to provide, in systems of the aforementioned type, inst-rumentalities whereby the volume of sound reproduced from a composite soundpicture film may be'controlled from a point remote from the projecting apparatus, without causing the introduction of extraneous noises.

In one commercial embodiment of my invention, I attain certain of the above-mentioned objects by utilizing a photo-electric cell that is particularly sensitive to monochromatic light and which gives an output that bears a straight-line relation to the intensity of the light falling thereon. The monochromatic light source is preferably provided with a continuously variable, stepless, intensity-controlling device, such as a rheostat, and the light is plane-polarized before it is allowed to pass through a limitin%device to the film.

y varying the intensity of the light before it passes through the film to the photoelectric cell, entirely satisfactory sound-out volumecontrol is obtained, during reproduction, without the introduction of noises such as are caused when 'a volume-control device of any type is associated with the amplifier itself.

It is also feasible to alter the light intensity, during the recording process, in order to prevent over or under-modulation of the li ht by unusual sounds.

he polarized, monochromatic light is diffracted to only a small extent in passing through the limiting device, and, consequently, the boundary of the instantaneously illuminated portion of the film is more sharply defined than if unpolarized, polychromatic li ht is utilized.

T e use of polarized, monochromatic light is also valuable in recording the sounds photographically on the film, a phase of my invention that will be referred to later in more detail.

Although it is desirable to employ polarized light, my invention is also applicable to light from any convenient source, when such light is used to energize a photo-electric cell in the reproduction of sound-picture films or sound-films alone. In the event that polychromatic light is used, either polarized or unpolarized, it is desirable that the photoelectric cell shall be of the type that has a substantially straight-line response to light energy, over a fairly wide range of light intensity.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, to-

- gether with further objects and advantages thereof, will best be understood by reference to the following description, taken in connection with the accompanying drawing.

v The single figure of the drawing is a diagrammatic view of the reproducing portion of atranslating system, embodying a preferred form of my invention.

The apparatus illustrated in the drawing comprises an upper-film magazine 1, and a lower-film magazine 2. A film 3, which is initially carried by the magazine 1, is withdrawn therefrom, during the projecting process, by the action of a lurality of small toothed rollers 4, 5, 6 and and passes successively through a plurality of guiding devices 8 and 10.

The film is caused to advance through the guiding device 10 in a step-by-step manner by mechanism familiar to those skilled in the art (not shown), the pauses between successive steps being for the purpose of permitting light from a source 11 to pass therethrough and form enlarged images on a screen 12.

' The motion of the film through the guiding device 8 is continuous. The means for reproducing the sound is, accordingly, disposed adjacent to the said device and comprises a source 13 of monochromatic light supplied with energy from a battery 14 under the control of a rheostat 15. As mentioned previously, the rheostat is preferably so placed that it may be operated rom a position in the audience, and I have, according- 1y, illustrated it as located intermediate the screen 12 and the projecting camera.

A lens system. exemplified by the lens 16, concentrates the light from the source 13 and causes it to pass, in a relatively narrow beam, through a polarizing device 17. A limiting device 18, such as a shield having a fine opening 20 therethrough, or a knife-edge, is interposed between the polarizing device 17 and the film, and a reduced image of the opening is focused on the film by an appropriate optical system, exemplified by a single lens 21.

A light-sensitive element such as a photoelectric cell 22, having an anode 23 and a cathode 24, is so disposed adjacent to the guiding device 8 that the light, which passes through the sound portion of the film, falls on the cathode. A source 25 of biasing potential for the photoelectric cell is provided, the negative terminal thereof being connected to the cathode and the positive terminal thereof being connected to the anode through the primary winding of an audiofrequency transformer 26 that has a resistor 27 connected in shunt thereto. The secondary winding of the transformer is'comprised in the input circuit of an audio-frequency amplifier 28. The amplifier may be of any conventional type comprising power-tubes inter-connected by transformers or resistors. The so-called push-pull amplifying system is to be preferred, rather than the simple cascade connection, since it gives an output that is less prone to be distorted. Neither the separate elements of the amplifier nor the several voltage sources required therefor, are shown these elements being believed sufliciently well known to those skilled in the art to obviate the necessity for illustration.

The output circuit of the amplifier is connected to a loud speaker 28, or a plurality of loud speakers (not shown), preferably disposed behind the screen 12 upon which the moving pictures are being projected.

The manner in which the photo-electric cell is connected to the amplifier constitutes no part of the present invention, it being quite feasible to connect it thereto through a high-resistance element rather than through a transformer, as shown.

In the operation of the reproducing ortion of a translating system just descri ed,

the light from the source 13 reaching the photo-electric cell 22 is caused to vary, in amount or intensity, by the passage of the sound-recordportion of the film. The output of the photo-electric cell, within reasonable limits of illumination, varies directly with the said illumination and gives rise to pulsating direct currents in the primary of the transformer 26. The pulsating currents, in turn, induce alternating currents corresponding thereto in the secondary of the transformer, thus energizing the thermionic amplifier and causing it to deliver an output current representative of the light variations and, consequently, of the photographically recorded sounds.

The sound-record portion of the film may be either of the constant-density, variablearea ty e, or it ma be of the variable-density type, he type 0 record is substantiall immaterial, in so far as the effect upon the p oto electric cell is concerned.

The polarizing device is preferably so arranged that the light is polarizedin a plane parallel to the lon est dimension of the opening 20, in the limiting device 18, or parallel to the opening in the guiding member 8 when such opening, or slot, is utilized as a limiting device. When polarized in this manner, the monochromatic light is not diffracted to as great an extent by the edges of the minute slot in the guiding device as unpolarized light would be. Consequently, the area of the portion of the moving film which is illuminated is more clearly defined, and the quality of the reproduced sounds is consequently im-- proved.

It has been proposed by previous workers in the art to vary the volume and intensity of the sound produced by the loud speaker by adjusting either the filament-heating potential applied to the amplifier tubes the grid-biasing potentials applied to certain of the said tubes, or the plate potential supply to them. I have found these control systems to be unsatisfactory, no matter how carefully handled. Thermionic tubes are potentially operated devices, and such voltage re-adjustments invariably cause the loud speaker to emit unpleasant sounds, indicative that the sound-volume is being changed.

According to my invention, the amplifier adjustment is not alteredduring the projection of a sound record,but the volume of sound coming from the loud speaker is controlled by merely varying the intrinsic brilliance of the light source. This method of control does not cause the loud speaker to give out unpleasant sounds, and has the added advantage that it may be accomplished from any convenient location.

It lies within the scope. of my invention to utilize any convenient source of polychro- Irrespective, however, of the presence or abf sence of the polarizing device, or whether monochromatic or polychromatic light is used, the rheostat or analogous instrumentality associated with the light source is utilized for the purpose of obtaining satisfactory control of the volume of the sound produced by the loud speakers.

Although I have illustrated my invention in connection with the reproducing portion of a translating system, it is not restricted thereto, but is of marked value in the recording portion.

At the present time, photographic soundrecording systems for the making of talking-movie films may be-roughly divided into three broad classes.

In one class, the light from an unvarying source is variably eclipsed by a mechanical, sound-actuated device, such as a shutter.

In another class, the light from an unvarying source, instead of being eclipsed by a shutter, is caused to travel in and out with reference to the edge of the film, producing a serrated exposed porton of constant densit In still another class, the light from a constant source is polarized, the plane of polarization is caused to'rotate by a Kerr cell, in

response to sound, and the light is then passed through an analyzer to the film.

In systems of the type wherein the light is mechanically controlled, it has been found advisable to either concentrate the light by an optical system in a fine line on the film or to provide a slot closely adjacent to the film in order to limit the area of exposure. Whenever thelight passes through a narrow slot or travels pas t the edge of a mechanically-actuated shutter, it is diffracted to a certain extent, and the boundaries of the exposed portions of the light-sensitive element, or film, are blurred.

My invention, therefore, is also applicable to recording systems of the type wherein. the light is mechanically controlled, it having been found that, when monochromatic, polarized, light is utilized instead of light from a source of the usual type, diffraction-phenomena are noticeably lessened.

It has also been found advantageous to provide the light source, in recording, with a rheostat or analogous device, since, by the proper manipulation of such a rheostat, the

exposure of the film, if made according to the variable-density system, may be so controlled that extraordinarily loud sounds are toned down in the process of recording. At the same time, by increasing the intensit of the light source, weaker sounds may be etter recorded.

The application of my invention to recording systems should be sufliciently obvious, after a careful consideration of the foregoing description of its application to the reproducing portion of a translating system, to make further illustration unnecessary.

Although I have illustrated only a single commercial embodiment of my invention, numerous modifications thereof will be apparent to those skilled in the art. My invention, therefore, is not to be limited except insofar as is necessitated by the prior art or by the spirit of the appended claims.

I claim'as my invention:

1. In a sound-reproducing system, a source of substantially monochromatic light, means for causin a sound record to move adjacentto said light source, light-sensitive means so disposed as to be influenced by light from said source after it has been modified by a sound record, means for limiting the area of a sound record exposed to light from said source, and polarizing means interposed between said light-source and said limiting means, whereby diffraction phenomena occasioned by said limiting means are lessened.

2. In a sound-translating system, a source of substantially monochromatic light, a light-sensitive element, a screen having a narrow aperture therethrough interposed between said source and said element, and light-polarizing means interposed between said source and said screen, whereby diffraction phenomena occasioned by said aperture are lessened.

3. In a sound-translating system, a source of substantially monochromatic light, a light-sensitive element, a screen having a narrow aperture thercthrough interposed between said source and said element, and means interposed between said source and said screen for polarizing the light from said source in a plane parallel to the longest dimension of said aperture, whereby difi'raction phenomena occasioned by said aperture are lessened.

In testimony whereof, I have hereunto subscribed my name this 7th day of J anuary, 1928.

BERNARD J. KROGER. 

